A method to derive long-term coastal wind data from distant weather station to improve aeolian sand transport rate prediction

Aeolian sediment transport on beaches is responsible for dune growth and/or recovery. Models predicting potential aeolian sediment transport rates often overpredict the amount of deposition on the foredune when applied to narrow (<100 m) beaches, pointing to supply limitations. Our goal is to better understand these limitations, especially in the long-term (>years) in order to improve predicted transport volumes and the timing of transport. Here, we used 8 years of Argus video images at Egmond aan Zee, The Netherlands, in combination with routine weather data to delineate 241 limited from 467 unlimited sand transport events to explore supply-limiting factors. Our research shows that the wind is more oriented to the west (shore normal) and is generally stronger for limited transport events. This indicates that the available fetch distance is often less than the critical fetch needed for unlimited transport. This is further confirmed by the timing of the transport events, as limited events often became unlimited during low tide when the beach was the widest and fetch potentially the longest. Our results help understanding the nature of aeolian sediment transport on narrow beaches, which will hopefully lead to better predictions of annual aeolian sediment transport rates.

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Consequences of a Storm Surge for Aeolian Sand Transport on a Low-Gradient Beach

Journal of Marine Science and Engineering ◽

10.3390/jmse8080584 ◽

2020 ◽

Vol 8 (8) ◽

pp. 584

Author(s):

Jorn T. Tuijnman ◽

Jasper J. A. Donker ◽

Christian S. Schwarz ◽

Gerben Ruessink

Keyword(s):

Storm Surge ◽

Volume Growth ◽

Primary Source ◽

Beach Sand ◽

Sand Transport ◽

Strong Wind ◽

Aeolian Sand ◽

Aeolian Sand Transport ◽

Wind Events

Wind-blown beach sand is the primary source for the volume growth of the most seaward dune, the foredune. Strong wind events can potentially dominate long-term aeolian supply but in reality do not contribute considerably because they often coincide with a storm surge. The aim of this paper is to further our understanding of how a storm surge prevents or severely restricts aeolian supply. Using field data collected on the 1:50 sloping Egmond beach (Netherlands) in the aftermath of a 1-m storm surge, we show that the ground water in the upper beach rose to well above normal levels during the surge, which resulted in the development of a seepage face during falling tide and hence persistent saturation of the emerging beach. Using a fetch-based model, we predicted aeolian supply during the 2-day surge period to be about 66% of the potential supply. Fetch limitations imposed by the surge-induced inundation and the continuous saturation of the sand on the emerging beach both contributed to the predicted supply limitation. Our results quantitatively support earlier studies that suggested surges to be the primary condition that causes predictions of long-term potential foredune growth to overestimate measured growth.

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Using Video Monitoring to Test a Fetch-Based Aeolian Sand Transport Model

Journal of Marine Science and Engineering ◽

10.3390/jmse8020110 ◽

2020 ◽

Vol 8 (2) ◽

pp. 110 ◽

Cited By ~ 1

Author(s):

Pam Hage ◽

Gerben Ruessink ◽

Zilla van Aartrijk ◽

Jasper Donker

Keyword(s):

Wind Velocity ◽

Transport Model ◽

Transport Rate ◽

Beach Sand ◽

Sand Transport ◽

Winter Period ◽

Aeolian Sand ◽

Aeolian Transport ◽

Aeolian Sand Transport ◽

Strong Winds

Transport of beach sand to the foredune by wind is essential for dunes to grow. The aeolian sand transport rate is related to wind velocity, but wind-based models often overpredict this transport for narrow beaches (<100 m). To better predict aeolian sand transport, the fetch-based Aeolus model was developed. Here, we qualitatively test this model by comparing its transport-rate output to visual signs of aeolian transport on video imagery collected at Egmond aan Zee, the Netherlands, during a six-month winter period. The Aeolus model and the Argus images often agree on the timing of aeolian transport days, except when transport is small; that is not always visible on the Argus images. Consistent with the imagery (minimal signs of aeolian activity in strong winds), the Aeolus model sometimes predicts the actual transport to be smaller than the potential transport. This difference is largest when wind velocity is large, and its direction is cross-shore. Although transport limitations are not predicted to be common, the results suggest that their effect on the total transport in the study period was substantial. This indicates that the fetch distance should be taken into account when calculating aeolian transport for narrow beaches on longer timescales (>weeks).

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Transports éoliens réels et théoriques en haut de plage et sommet de dune (Wissant, Pas-de-Calais, France) / Observed and predicted rates of aeolian sand transport on the upper beach and dune top, Wissant beach, Northern France

Géomorphologie relief processus environnement ◽

10.3406/morfo.2002.1155 ◽

2002 ◽

Vol 8 (4) ◽

pp. 321-334 ◽

Cited By ~ 1

Author(s):

Catherine Meur-Férec ◽

Marie-Hélène Ruz

Keyword(s):

Sand Transport ◽

Aeolian Sand ◽

Northern France ◽

Aeolian Sand Transport

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